Radeon 4850 graphical glitch + workaround

[KenTWOu]

I have Palit Radeon HD 4850 Sonic 512MB, Win 7 x64, Catalyst 13.1. Judging by system requirements 4850 isn't officially supported by the game. So right from the get-go the game has weird graphical glitches, some of the objects flicker, weird shapes appear out of nowhere. Here are the shots:

Spoiler below!

I found a way to get rid of these glitches:
1) turn on Debud Menu using this guide.
2) once in the game press F1 and turn off Occlusion Culling:

Spoiler below!

P.S: there is one problem though, some earlier underwater segments have minor glitches without Occlusion Culling. E.g. ground surface flickers in a few places outside Lambda station. So when that happens turn OC on and then turn it off again when get inside.